1. Field of the Invention
The invention relates generally to the field of epidural needles and methods of using the same.
2. Background Art
In general there are two methods for administering epidural anesthesia. The first is by means of a straight epidural needle connected at its proximal end to a syringe or other source of liquid anesthesia. The second is by means of a curved-tip epidural needle used to introduce an epidural catheter into the epidural space, which ranges on the order of 2-7 mm in width.
Straight epidural needles employed in the former procedure do not require the passage of a catheter. They typically have a straight distal end and a gauge size on the order of 21-22 gauge (iso-9626). Curved-tip epidural needles, through which a catheter is introduced, of necessity are somewhat larger, having a gauge size typically on the order of 17-18 gauge (iso-9626).
Curved-tip epidural needles, used for introducing a catheter into the epidural space, possess a curved tip so that the distal end of the catheter can curve upward for proper placement within the epidural space, rather than perpendicularly abutting the dura matter, the delicate membrane lying over the arachnoid and pia matter covering the spinal cord.
The epidural needles of the curved type currently in use are of two kinds: (1) those curved to have an inclined surface on the order of 7xc2x0 from the longitudinal axis (known asxe2x80x9cTuohyxe2x80x9d epidural needles); and (2) those curved to have an inclined surface on the order of 12xc2x0 from the longitudinal axis (known as xe2x80x9cHustedxe2x80x9d epidural needles.)
Whether the procedure is of the type wherein the anesthesia is introduced through a syringe attached to the epidural needle or of the type where the anesthesia is introduced through a catheter, great care must be taken to avoid puncturing the dura mater and thus permitting spinal fluid to leak out.
In a typical procedure, a local anasthetic may first be given to minimize pain and discomfort from the epidural needle. With the stylet in the needle, the needle is slowly and carefully inserted until it abuts the ligamentum flavum, at which time the anesthesiologist senses an increase of resistance to further insertion. At this time, the stylet is removed from the needle and axe2x80x9closs of resistancexe2x80x9d syringe is attached to the luer fitting of the needle hub. By slowly advancing the needle and syringe while simultaneously applying pressure to the syringe piston, the ligamentum flavum is penetrated and the needle is advanced into the epidural space where loss of resistance to the syringe piston is confirmed.
At this point, the syringe is removed and the epidural catheter is inserted through the needle until the distal end of the catheter exits the curved tip of the needle and is inserted the desired distance into the epidural space.
The proximal end of the catheter is then placed in fluid communication with a source of the anesthetic drug to be introduced. Typically, this is done by securing the proximal end of the catheter within the distal end of an adapter and securing a syringe containing the anesthetic drug to the proximal end of the adapter.
U.S. Pat. No. 4,141,365 discloses a tissue stimulation apparatus for positive positioning of an electrode-bearing lead proximous to tissue which is to be stimulated electrically, the invention particularly includes a body penetration and insertion assembly which carries an elongated flexible strip of physiologically inert plastic material having at least one electrode positioned thereon into contacting relation with said tissue. The insertion assembly comprises a hollow needle having a slot formed longitudinally along the length of one wall thereof, the slot allowing transverse removal of the flexible lead from the needle after proper positioning of the lead and after removal of the needle from the body. The slotted assembly allows use of a flexible electrode lead having electrical connections at the external end thereof which are too large to pass through the hollow needle. U.S. Pat. No. 4,141,365 is incorporated herein by reference in its entirety.
U.S. Pat. No. 4,721,506 discloses an epidural needle and method of use involving a needle shaft having a first end and a second end with an axial channel extending therebetween. The first end of the needle shaft includes an inclined surface and a rounded and blunted point. The second end of the needle includes an attachment means. A solid rod having an inclined surface and a rounded and blunted point is receivable into the axial channel of the needle shaft. When the solid rod is positioned within the axial channel of the needle shaft, the point of the solid rod and the needle together form a unitary tip having an inclined portion and a blunted portion. The blunted portion forms an end face disposed at an angle of about 80 to 100 degrees relative a longitudinal axis of the needle. The unitary tip avoids nicking, piercing, severing, or perforating the veins, arteries, nerves and dura of the patient in traversing the spinal ligaments and in entering a space proximate the dura matter of a spinal cord of a patient to provide liquid communication with the space when the solid rod is withdrawn from the axial channel of the needle. U.S. Pat. No. 4,721,506 is incorporated herein by reference in its entirety.
U.S. Pat. No. 4,808,157 discloses a needle that is a multi-lumen needle and preferably a dual-lumen epidural-spinal needle. The needle is provided with a hub, which allows for attachment of a syringe to one or more of the lumina, or alternatively the attachment of an adapter to which a syringe can be attached. Preferably the lumina have different cross sectional areas. The smaller of the lumina should be of sufficient size to allow a spinal needle, guide wire, or microcatheter to be inserted through the lumen. The larger of the two lumina should preferably be of sufficient size to allow an epidural catheter, spinal needle or guide wire to be introduced. The needle of the present invention has applications of regional anesthesia, chronic and post operative pain management, cricothyroid puncture, intracerebroventricular puncture and, access and drainage of concealed fluid collections within the body. U.S. Pat. No. 4,808,157 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,425,717 discloses a system for administering epidural anesthesia utilizing an epidural catheter permanently secured at its proximal end to an adapter for putting the catheter in fluid communication with a source of liquid anesthesia. The system employs a splinable needle for inserting the catheter into the peridural space. U.S. Pat. No. 5,425,717 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,573,519 discloses an elongated, hollow spinal needle that is less prone to causing postdural puncture headache by having a modified, pencil-like point with a rounded shoulder at the juncture between the modified, pencil-like point and the body of the spinal needle. A side port is formed in the hollow needle at a position adjacent the rounded shoulder. The leading edge of the side port is located not more than 1.5 times the external diameter of the hollow needle from the tip of the pencil-like point to reduce the bending moment between the tip and the side port. The cross sectional area of the side port is configured to be equal to or incrementally larger than the cross sectional area of the lumen of the hollow needle. U.S. Pat. No. 5,573,519 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,628,734 discloses various embodiments of spinal needles, each having a curvature, that are used in a method of administering a spinal anesthetic while preventing the development of post dural puncture headache. U.S. Pat. No. 5,628,734 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,843,048 discloses an epidural needle through which an epidural catheter may be threaded for administering liquid anesthesia into the epidural space, the needle having a curved distal end, the tip of the needle distal to the opening in the needle shaft being substantially planar at an angle of 80xc2x0-100xc2x0 relative to the curved longitudinal axis of the needle shaft, the needle tip being characterized as being faceted so as to retard inadvertent passage of the needle tip through the dura mater of a patient while at the same time retaining the sharp cutting edges common to a like epidural needle which has not had its tip so treated. U.S. Pat. No. 5,843,048 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,848,996 discloses a double-hole pencil-point (DHPP) spinal needle that is composed of a closed end blunt ogival or pencil point tip and two circular coaxial holes in close proximity to the tip. Anesthetic solution may be injected through the coaxial holes in a direction parallel to the long axis of the spinal fluid column which allows an even anesthetic distribution with a low dosage required. The spinal needle allows anesthetic solution to be injected even when one of the holes is obstructed by a tissue fragment and rapid reflux of cerebral spinal fluid at twice the rate of single bole pencil point spinal needles. U.S. Pat. No. 5,848,996 is incorporated herein by reference in its entirety.
In some embodiments, the invention relates to a needle comprising a hollow shaft having opposed distal and proximal ends, the hollow shaft having a lumen extending from the proximal end of the shaft and terminating at an opening on a top of and proximal to the distal end of the needle shaft. The hollow shaft is adapted to receive an epidural catheter for introducing liquid anesthesia into the patient which can be threaded through the proximal end of the needle until a portion of the catheter exits through the lumen opening on the top of the distal end of the needle shaft; and a cutting surface at the distal end of the hollow shaft adapted to be inserted into a patient, wherein the cutting surface is on the bottom of the distal end of the hollow shaft.
In other embodiments, the invention relates to a method of installing a catheter in the epidural space comprising pushing a needle into the epidural space with a cutting surface of the needle substantially parallel to the dura fibers of the patient, wherein the needle comprises a substantially straight cutting surface, feeding a catheter through the needle and into the epidural space, removing the needle, while holding the catheter stationary, and securing the catheter.
Advantages of the invention may include one or more of the following:
Providing a needle that avoids inadvertent penetration through the dura mater and into the subarachnoid space, causing spinal fluid to leak out;
Providing a needle that avoids the onset of postdural puncture headache;
Providing a needle that limits the number of dural fibers that are cut during use;
Providing a needle that has a cutting edge that is parallel to the dural fibers; and
Providing a needle that has an increased sensitivity to the loss of resistance which can be used for detection of the epidural space.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.